Engines, including diesel engines, gasoline engines, natural gas engines, and other engines known in the art, exhaust a complex mixture of combustion related constituents. The constituents may be gaseous and solid material, which include nitrous oxides (NOx) and particulate matter. Due to increased attention on the environment, exhaust emission standards have become more stringent and the amount of NOx and particulate matter emitted from an engine may be regulated depending on the type of engine, size of engine, and/or class of engine.
Engineers have come to recognize that undesirable engine emissions, such as NOx, particulate matter, and unburnt hydrocarbons, can be reduced across an engine's operating range with fuel injection systems with maximum flexibility in controlling injection timing, flow rate, injection quantity, injection rate shapes, end of injection characteristics and other factors known in the art. However, it has also been observed that an injection strategy at one engine operating condition may decrease emissions at that particular operating condition, but actually produce an excessive amount of undesirable emissions at a different operating condition. Thus, for a fuel injection system to effectively reduce emissions across an engine's operating range, it must have the ability to produce several different rate shapes, have the ability to produce multiple injections, and produce injection timings and quantities with relatively high accuracy. Providing a fuel injection system that can perform well with regard to all of these different parameters over an entire engine's operating range has proven to be elusive.
In order to reduce hydrocarbon emissions, one strategy has been to seek an abrupt end to each injection event. This strategy flows from the wisdom that reducing poorly atomized fuel spray into the combustion chamber toward the end of an injection event can reduce the production of undesirable hydrocarbon and smoke emissions. In the case of fuel injectors equipped with direct control needle valves, an abrupt end of injection is often accomplished by applying high-pressure fluid to the back side of a direct control needle valve member to quickly move it toward a closed position while fuel pressure within the injection remains relatively high.
In one example common rail fuel injector disclosed in U.S. Pat. No. 6,814,302 to Stoecklein et al, a needle control chamber has one outlet and one inlet. At the end of injection the inlet fills the needle control chamber. A bypass conduit, which feeds first into a valve chamber and then into the outlet, may provide additional fuel flow to the needle control chamber. The use of a bypass conduit that feeds into the valve chamber and then the needle control chamber outlet has a drawback of inevitably affecting the start of injection. Moreover, the valve and valve chamber required to facilitate the bypass conduit add cost and variability to the operation of the injector.
The disclosed fuel injector with auxiliary filling orifice is directed to overcoming one or more of the problems set forth above.